One classification that may be made of curemeters would include devices wherein one of two heated dies is rotated or oscillated with respect to the other, and the resulting torque of the sample measured. Among prior art patents in this group would be
______________________________________ Veith et al U.S. 3,488,992 (1970) Uremo et al U.S. 3,479,858 (1969) Barker et al U.S. 4,552,025 (1985) Burnin et al U.S. 5,079,956 (1992) Putnam U.S. 4,953,406 (1990) Danko et al U.S. 4,343,190 (1982) Tosaki U.S. 4,584,882 (1986) ______________________________________
A second type of curemeters, and one to which the present invention primarily addresses itself, would include devices which utilize two dies, and additionally a third, rotor, member which is oscillated to derive the required test results. This group would include
______________________________________ Prewitt et al U.S. 4,546,438 (1985) Harris et al U.S. 3,531,996 (1970) Decker U.S. 3,681,980 (1972) Price et al U.S. 4,421,424 (1983) Turner et al U.S. 4,275,600 (1981) Wise U.S. 3,387,490 (1968) Beatty et al U.S. 3,182,494 (1965) Kitchen U.S. 4,559,812 (1985) ______________________________________
Several common threads run through the disclosures of the above-mentioned test devices: the test sample materials are located on top of as well as under the rotor head, i.e. the rotor head is embedded within the rubber samples during testing; and no means are provided for sealing off the sample material from the lower die. (Additionally, in the U.S. Pat. No. 5,221,500 to Gent (1993), there is no test cavity enclosed by a pair of dies, but rather the rotor impinges directly upon the wall of the article being cured).
When a test device of the above type is opened, a substantial labor- and time-consuming effort is required to remove the sample therefrom. In practice, it is found necessary to employ metal bars and other tools to break the cured rubber from around the embedded rotor head, and this effort frequently results in tearing of the sample. This then necessitates the disassembly of the rotor from the curemeter to complete the removal of the sample, and the cleaning of any detritus which may have collected around the rotor shaft and die. When the rotor is again inserted, it is extremely difficult to seat it at exactly its former level. Thus, while the previous series of test samples may have yielded a family of test curves fairly closely related, when the testing continues with the rotor replaced, at even a slightly different height, a new curve-series will be generated, slightly differently located. This will be further referred to hereinbelow.
The above procedures unnecessarily prolong the time the device must remain open before it is recharged with a new sample, and the result is a loss of heat which must be recovered when the device again closes. Furthermore, without the heat sink means of the present invention to provide some temperature control, unacceptable heat losses are also experienced from the rotor through its associated drive- and support-means.
The results of these shortcomings are that the successive testing of samples shows poor reproduceability of results, with test curves, as seen hereafter, which are not closely bunched together.